1. Field of the Invention
This invention relates to adhesively secured fasteners utilizing quick-setting, photocuring adhesives.
2. Background Art
U.S. Pat. Nos. B1 5,044,853 and 5,277,530 show a fastener for quick attachment to a substrate. The fastener is simply depressed against the substrate and a quick-setting adhesive is dispensed into the interface between the fastener and the substrate thereby attaching the fastener. Anaerobic and several other adhesives may be used quite satisfactorily with such fasteners.
However, there are some situations where it has become desirable to utilize a photocuring adhesive rather than those previously used. As used herein, a photosensitive adhesive is one which cures upon exposure to radiation in the visible and ultraviolet light spectrums.
Utilizing photocuring adhesives requires that the adhesive be effectively shielded from the curing radiation, otherwise the adhesive will cure prematurely in the fastener rendering the fastener useless. At the same time, when the fastener is pressed against the substrate to which it is to be secured, it must be possible to illuminate the adhesive at the interface between the fastener and the substrate to cure it. As used herein, the term xe2x80x9cilluminatexe2x80x9d includes radiation in the visible and UV spectrums.
I have discovered approaches which render use of a photocuring adhesive feasible in fasteners of the general type shown in the aforesaid patents. In one embodiment, the adhesive is stored in a reservoir made of UV opaque material which is placed in a UV transparent fastener such that upon expelling the adhesive into an interface between the fastener and the substrate to which the fastener is to be secured, UV light can contact the adhesive in such interface to effect the cure.
In another embodiment the fastener has a UV opaque chamber in which the adhesive is stored, and the portion which forms an interface with the substrate is sufficiently transparent to UV radiation that adhesive expelled into the interface from such chamber can be cured. In still another embodiment, the fastener is opaque to the UV spectrum, but is used on UV transparent substrates, such as glass or clear plastic, such that UV radiation may reach the photocuring adhesive in the interface between the fastener and the substrate by having the light pass through the substrate beneath the fastener.
In another embodiment, the adhesive reservoir and plunger are made of a material which is opaque to UV radiation but at least one of them is transparent to visible light, whereby the reservoir when filled with adhesive and stopped with a plunger may be visually inspected to determine whether it contains adhesive. Other embodiments which may be combinations of the aforesaid will become apparent as this description proceeds.
I have also discovered that adhesion of the fastener to the frit-covered margin of a vehicle window may be improved by coating such margin with a primer. Several primers useful for this purpose are described herein.
Apparatus for affixing self-dispensing UV curable adhesive fasteners on windows to be installed in automotive vehicle bodies is also disclosed. Such apparatus includes applicators for holding the fasteners and pressing them against the window and a light source in each applicator which will direct light through a transparent flange of the fastener to cure UV curable adhesive disposed between the flange and the window. The apparatus also includes a fixture for holding the window in a determined position relative to the applicator so that the fasteners held by the applicators will be affixed to the window in predetermined locations. The applicators may be so constructed and arranged that the UV radiation will be shielded from the eyes of personnel working at the fastener applying apparatus.